Shown above is the original Astron Sprint.
This rocket was later given my "Iris" modification, which extends the body tube about 5 inches above the streamer/parachute bay, and allows for a payload with an Altimeter One to measure altitudes. The Iris payload is named after the Greek god of the rainbow. She is a messenger of the gods, linking the gods with humanity.
Shown here is the original Iris payload addition, yellow, which was lost along with the electronics.
Originally, I replaced the flimsy crepe paper streamer with a plastic one, but the plastic seems to stick to body tube because of static electricity, so I replaced it again with a small 8" parachute. With this parachute it descends at about 11 mph, soft enough for a safe grass landing. The rather small size should prevent this from drifting too much - a real problem considering the height it can attain.
This picture shows the latest incarnation of the Astron Sprint Iris, after the payload section and nose cone were rebuilt. It is a bit shorter than the original payload, so it may indeed get that last twelve inches of altitude I am trying for. (Read the logs and you'll understand why.) Note that if you look very closely you can see that the new nosecone (from Balsa Maching Service) is not exactly like the original shape, but it is close enough to fly.
This rocket currently holds the all-time altitude record for any rocket in my fleet: 1199 feet. This rocket has flown higher than the NY Times Building in NY, the John Hancock Tower and the Aon Center in Chicago, and every other rocket I built and flew.
This model is one of four rockets I have flown with the B6-6 motor. This model performed the best, travelling 125 mph and reaching an apogee of 559 feet.
I have flown this model and eleven others on the C6-5 motor. This model reached the highest apogee of 1198 feet. There was no accelerometer on board to measure the speed however.
This is also one of four models I have flown with the C6-7 motor. The March 2012 flight reached 1199 feet, which is my current all-time altitude record of any model. During that flight it also reached a speed of 197 mph (not a record).
SPECIFICATIONS
Series Number: 9
Number of Stages: 1
Stock Length: 13.8"
Iris Payload Length: 3.125"
Total Length with Iris: 16.925"
Diameter: 0.976"
Fin Circle Span: 4.976"
Stock Empty Weight: 30.5 grams
Iris Payload Weight: 9.8 grams
Empty Weight with Iris: 40.3 grams
Liftoff Weight Range: 62.2 - 71.4 grams
Motor Diameter: 18 mm
Motor Length: 70 mm
Motor Retention Method: Friction Fit
Payload Interior Length: 2.75"
Payload Interior Diameter: 0.95"
Payload Volume: 1.95 cubic inches
Altimeter Capable: Yes
Recovery Method: 8" Plastic Parachute
Alternate Recovery: 4' Paper Streamer
Typical Descent Speed: 11 mph (parachute)
Recovery Protection Method: Nomex Sheet, 3"x3"
Shock Cord Mount: Paper
Noseweight: Washer on Nosecone Base
Nosecone Material: Balsa Wood
Number of Fins: 3
Fin Material: Balsa Wood
Unique Features: Drag-reducing Boattail, Eliptical Nosecone, Eliptical Fin shape
Launch Lug Size: 1/8"
Paint Used: Pactra Aero Gloss Dope
Completion: about 1977
FLIGHT LOGS
(Estimated about 3 flights on this rocket back in the 1970's)
2010, November 13: Tanguy Soccer Field, light wind
A8-3: Good Flight & Recovery. Altitude is an estimated 163 feet, there was no altimeter onboard.
2011, May 29: Indiantown Gap, Light to moderate wind
B6-4: Nice flight, pretty high. Streamer singed a little, drifted fairly far - uncharacteristic for a streamer, but winds were up. Will replace crepe paper streamer with a shorter, plastic streamer and go for a maximum-altitude C flight with onboard altimeter. Thr altitude was estimated as 460 feet, there was no altimeter onboard.
2011, July 2: Indiantown Gap, Light to moderate wind
A8-3: First low-power test with the new altimeter payload section, it returned with a reading of 162 feet. It was a good flight and recovery, but the streamer appeared to stick and wrap around rocket and shock cord. Plastic appears to not be a good material for streamers. Further flights proved that indeed, it is not.
B6-4: Sailed out of sight, plastic streamer trouble again: Seems to wrap around shock cord and stick to body tube from a static charge. Altimeter read 457 feet.
2011, July 3: Indiantown Gap, Light to moderate wind
C6-5: Nervous because of light but shifting winds this morning, model could have drifted very far, as it has before. Incredible altitude on this bird. Perfect flight. Again, plastic streamer proves a bit too 'static-y' for reliable use, wrapping around and sticking to shock cord and body tube. Came down too fast for my liking, but may have saved this from being lost. Reached a record apogee of 1198 feet!
2011, August 7: Halifax, calm to light wind
2011, August 25: Penn Manor, Moderate wind
B6-4:The Sprint was on a mission carrying an Iris payload with an Altimeter Two. She left the pad very quickly and accelerated at 18.1 G's to a speed of 117 mph while turning somewhat towards the stiff breeze. 4.8 seconds later at 466 feet the small 8" parachute deployed. 0.3 seconds later she reached an apogee of 472 feet before descending at 9 mph. The flight lasted 38.4 seconds.
2011, December 4: Penn Manor, Steady 10 mph wind
A8-3: I had hoped to try for a record altitude on a C6-7, but it was way too windy. On this first flight of the day, I sent the old Sprint on a mission to see how the winds aloft were, since it was pretty breezy today. It was also carrying an Altimeter 2 to collect flight data to gauge performance on this smaller A motor. The launch went off as well as can be expected. I had hoped for at least 100 feet, and was surprised to reach 165 feet.The A8 burned for about 1/2 second, peaking the acceleration at 5.4 Gs and averaging 2.8 Gs on the powered flight. The Sprint remained upright and reached a speed of 58 mph despite the winds. It then coasted for 2.8 seconds to 165 feet then descended 7 feet before ejection 0.6 seconds later. The small 8" chute deployed well and it then floated down at 11 mph to land 12.8 seconds later near the launch area. Success!
2012, March 18: Penn Manor, Light wind
It reached a top speed of 197 mph, a record for this model. The ejection was at exactly 7 seconds at an altitude of 1192 feet while still coasting upwards. It reached its apogee 4/10 seconds later at 1199 feet - a new record for any model of mine, but 12 inches shorter than I had hoped for!
If the delay had only been a fraction of a second too long I could have broken the 1200 mark. The small 8" chute deployed and the rocket fell at 12 mph to land within a few hundred feet of the launch pad. Overall flight time was 1 minute and 12.5 seconds.
2012, May 6: Penn Manor, light wind
I suppose I was not at my best when I felt the need to brag to a fellow club member (who just launched a 3-stage Farside) that I went higher on a single motor than he did with three motors. Anyway, after apogee the Sprint only descended 23 feet in another 1.3 seconds before ejection at 1116 feet. The tiny 8" chute opened and the model descended at 11 mph to touch down perhaps a good 600 feet downwind.
The total flight time was 74.5 seconds. Not only did this rocket break its own speed record, it set a new record for flight duration for any flight of mine. That's my definition of a successful flight.
2012, May 26: Indiantown Gap, 5 mph wind
The liftoff went well, and it flew straight up and out of sight, but I was prepared by standing far back and watching the flight through binoculars. The problem was I was standing in the wrong spot and the rocket appeared to fly straight into the sun, causing me to lose sight of the coast and recovery deployment.
The rocket was spotted descending by a fellow club member and I tracked it to the ground across the street into some very tall grass where it was recovered.
Although it was painted bright yellow and the nose cone orange, it was near impossible to find it in the 3-foot tall grass in such a large field. I made many zig-zag steps through the field in a desperate attempt to find the payload with the $70 electronics inside. I would have sacrificed the altimeter to have the flight data, but that was just not to be.
With a storm approaching and thunder sounding in the distance, the search was aborted for safety reasons. The payload remains somewhere in the tall grass, now soaked from a good thundershower. 10% successful flight – I did get enough of the rocket back to determine the cause of failure. This was documented as the 13th flight of this rocket. Just sayin’
The Sprint Iris was repaired. A brand new nosecone and payload tube was made. This payload tube is a full inch and a half shorter. Instead of using a solid balsa bulkhead, I made one from a tube coupler and a small disk of plywood. The hollow tube coupler allows for more extra internal space, so the payload can be shorter. With the loss of the old payload and altimeter, I now am in the process of reinforcing all my screw-eyes with a short piece of Kevlar glued to the balsa and through the screw-eye, which should act as a backup if another screw-eye attachment fails. She is now ready to set some new speed and altitude records – hopefully.
2013, May 4: Halifax, 5-10 mph wind, 70 degrees
B6-6: It has been just shy of a year since I lost the original payload on the Sprint Iris. I have reconstructed a new payload section and was now ready for a test flight. The goal again was to reach a new altitude record and I hoped the slightly smaller payload section would allow that. First, I wanted to send up a lower-powered test flight to see how the winds were up there, so I selected a B6 motor. A previous B6 flight showed it could use a longer delay.
The motor lit and the rocket took off, travelling fast, straight and high. The one second burn peaked at 17 Gs at liftoff and averaged a healthy 6 Gs of acceleration. This got the Sprint to a speed of 125 mph, bleeding off for the next 5 seconds to an apogee of 559 feet – very good for a B motor. It then turned over and started to descend for the next 7/10 seconds, falling only 5 feet before the ejection charge fired at 554 feet. The B6-6 was perfect for this rocket.
The tiny 8” parachute opened and the rocket drifted down at 10 mph to land a few hundred feet away in tall grass. Flight time was 44.1 seconds. It was a perfect flight, but we had to spend at least a half an hour or an hour trying to locate it in the grass, very frustrating because it was such a perfectly clear and cool day for flying. I realized I need to pay closer attention to where this rocket landed.
C6-7: It was now time to go for the record altitude again. The previous B6 flight went well and showed that the new, smaller payload could very well make the difference and let this model break 1200 feet.
The C6 motor fired up and accelerated the Sprint to a record-high 19.4 Gs at liftoff. The motor burned for two seconds and averaged 4.8 Gs of acceleration, higher than any other C motor in this rocket. This brought the Sprint to a new speed record of 213 mph!
The ejection charge fired after 6.8 seconds, just a bit early, stopping the rocket’s upward coast a little early, at 1084 feet up. In the last 1/10 second the rocket halted its climb, gaining the last 23 feet of altitude where it reached its apogee of 1107 feet, far short of the record.
A good parachute brought this rocket back at 12 mph, landing in the tall grass again after a 67.3 second flight. It was a perfect and a spectacularly high flight. This particular C6 motor was a fast burner, creating record acceleration and speeds, but that was likely what prevented it from reaching a new altitude record. A slow burner could have done better.
This time I noted exactly the line from where I was standing and where the rocket landed. My wife, standing about 400 feet to the East, also noted a line where the rocket landed. We were able to pinpoint the exact area of the landfall, yet when we arrived there, the rocket was nowhere to be seen. It took another half hour before the rocket was found, after I gave up looking in circles and started an exhaustive (and exhausting) search in a large X-Y grid pattern. And yes, the rocket did land where we thought it did, but was still hidden in the grass. I decided it was time to fly only larger rockets in this field today, and I couldn’t risk any multi-stage rockets because the smaller booster stages would most certainly disappear from sight.
2013, June 30: Indiantown Gap, light wind.
C6-7: This was going to be the day, I could feel it. It was sooo…hot and humid and the winds were very light. I knew in this thin air I could finally break the 1200 foot mark, and still have this tiny rocket fall in the field. To make it more likely to happen just like that, I changed out my normal 8” hex chute for an even smaller 6” square chute – yes – square, with only 4 shroud lines.
The Sprint leapt off the pad at a powerful 18.6 Gs of acceleration, and for the 1.9 seconds of thrust it averaged 5 Gs. It attained a top speed of 209 mph before coasting for 6 seconds. Bummer the ejection fired a full second early, stopping this blistering pace but only after a rather long ½ second, where the rocket climbed an additional 12 feet, peaking at an apogee of 1183 feet. Another second of delay could have allowed an additional 17 feet and a new record altitude, but it was not meant to be.
Although it was way too high for me to see, someone else spotted the rocket’s little brown 6” parachute shimmering in the sunlight. It must have caught a thermal because the rocket descended at 11 mph but achieved a record-breaking flight duration of 76 seconds. Great flight!
B6-6: Another test flight using long-delay motors. This time I changed the parachute back to my usual 8” hexagon. (Parachutes are so much easier to pack then the stock paper streamer.)
Turning over at apogee, only 1/10 second went by before the ejection fired 5.4 seconds after thrust, with the rocket only falling 4 feet. The small 8” chute opened cleanly and the rocket came back at 15 mph. Flight time was 31.7 seconds. This was the second very successful flight of the Sprint today, and it wouldn’t be its last.
A8-3: Last flight of the day, it is getting entirely too hot. Rounding out the motor mix, this time I went with the smaller A8. Knowing there was no rush getting the Sprint back to earth, I selected a rather large 13.5” parachute for this flight.
The large parachute slowed the rocket’s return to a predictably slowest-ever speed of 7 mph. Flight time was 17.5 seconds. They should all fly this well, Sprint gave me three perfect flights today. After that, the club started packing up. Almost on cue, seconds after the equipment was all stowed, a deluge of rain struck.
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